This is an easy repair that readily lends itself to purchasing the $33 West System® epoxy kit—especially as that left side appears to be already part-way done!
I'd remove what's hanging loose and put in a backing plate of some kind.
With the West System®epoxy kit and a piece of flat plastic material, you can fabricate a new backing plate with the cloth provided. (It'll peel right off the plastic). Cut to a large oval shape to fit inside, sand the contact side of the backing plate—and hand-sand what you can reach of the interior. Coat with epoxy resin, and pull it into place with a screw-eye and bungee cord. (The metal "flux" brushes provided can be bent to coat the interior with the resin). Build up a layer or two of fiberglass "cloth" (provided) outside, and you're almost done. The West System® 300 filler that comes with the kit can be added last to make "fairing" the repair easier and more professional in appearance.
As this damage isn't extensive, you can probably dispense with the backing plate. But if you'd saved the piece that was cut from the inspection port installation, using part of it as a backing plate would make for a stronger repair.
I followed the above 3 part video steps to cover/get rid of the first of the three access ports that the previous owner cut out of the deck on "The Betty". I found the suggested steps helpful but will change a few things on the next 2 access ports.
First, I used a West Marine 10 ounce fiberglass cloth to build my laminate. Next time I'm going to use CSM (Chopped Strand Matt). I did some 6 inch by 6 inch test squares of both types as an experiment and the CSM produces a thicker, stiffer laminate for a given weight. So, that means fewer pieces you have to lay down for your laminate. Also, the CSM produces a better sanded surface.
Next, the 2nd video talks about making a fairing compound by using epoxy resin with West Systems 409. Thickening to the consistency of peanut butter is recommended. However, I found that this can produce small air bubbles (because the fairing compound is too thick) even if you are very diligent in mixing thoroughly and spreading firmly. The result is you sand your fairing flat but you still got little pits so this defeats the purpose of the fairing step.
However, I found a different approach that worked much better. That is, get your laminate as close to being built up to the level as you can, sand, then fill the surface and the few inevitable pits in your laminate with 409 (I only have West Systems 410 here in the US) mixed with epoxy but make it thinner. Only the consistency of ketchup. This process saves a step and the fact that your fairing compound is thinner eliminates the pits issue potential in your compound.
This process can be seen here... starting at 16 minutes in the video. I tried this process on part of my covering of the first access port and it worked much better than the fairing process described in the West Systems video.
Finally, particularly when using CSM, use a Fin Roller. This allows you get rid of all the tiny air bubbles much easier than using a brush. Plus, it allows you to spread the resin outward better than a brush. So, you can use less resin.
Much better than bindi would be some white Marine Tex or Formula 27, either will do a very good job of coming close to matching the hull color.
Cover the smoothed patch with some wax paper and carefully smooth again with a plastic spreader/scraper - you'll end up with a shiny patch that blends nicely with the hull, OR you can spray on some gelcoat or use the same technique as described for a near perfect finish. Wet sand & wax for perfection...