Start over, or fix?

Well, I went to finish up my new project, and I had to cut another hole in my finished project. Well.... I cut too low and I cut into a sub enclosure, and I had to cut another hole, but now there is a big 1inch deep hole in the rear of my enclosure (in the shape of a router cutout without the actual middle part out, but it did go all the way though on half of it that was NOT on the subenclosure).

Is it possible to seal this up, hopefully easily, or should I start over?

Related question, how close can a port be to the rear of a driver? Is 3 inches too close?
you could try bondo-ing your hole to make sure it's filled properly. or else try cutting out a 1.5" x 1.5" square hole in the enclosure and then cut a same size peice and fit it snugly, glue it in place, and use 1/8" hardboard cut about 2x2 over the fixed spot, glue that down and seal it up... sounds like it'd work.

as for what I have heard, 3" is the minimum you want in front of a port in an enclosure.
The port won't really care how close it is, as it will still be seeing the same box volume and pressure. Closer to the driver though and you will be getting more direct radiated sound which might muddy your midrange. Front mounted ports are affected less of course, but there's still reflection from the back wall that can come through. In past designs I've tried to put an angled brace (wrapped in foam) behind the port to block these out. Whether it made a difference, I'll never know, but it felt like a good path to take. :)

I've got my aunt's old pair of original Wharfedale Diamond bookshelf speakers somewhere. These things are tiny, the 1" diameter port is directly behind the woofer, you can actually read the details off the back of the magnet. Now, these weren't the highest of fi, but they could have put it somehwere else if necessary, so it's definitely not ruled out as a design no-no.