You might try putting some conductive ink in the nick. If it's only a single trace you broke, that might complete the circuit again. The other memory channel may not be stable, but it seems worth a try to me.
EDIT: For what it's worth, I rather wish I hadn't delidded my 3570K. My delid was successful and it dropped temps a lot, but I wasn't able to overclock even 100mhz higher and it destroys any resale value.
Believe me I tried all sorts of stuff with the assumption that I could possibly make it way worse and 100% unusable (or possible fix it with some dumb luck).
I tried to brush the area in different directions then covering damaged area with tape so that the lid would put pressure on it. Nothing...
I also tried the same thing but avoiding putting pressure on the area. Nothing...
Now I started to get desperate.
I tried to streak solder across in maybe 4 or 5 different directions. Nothing...
Finally I put a big glob in there, tried it but the glob got pulled off by the lid (and took more traces out with it).
At this point I was pretty confident the 1st ram slot was a goner. I tested, one last time to make sure it still works with at least one dimm and it did (luckily). I'm just going to relided everything and glue it with some high temp silicone.
I think after some thorough testing I may just keep the thing. Right now I have 2 x 8GB sticks of ram, going to return and swap for 1x16GB. So far all the benchmarks I've ran are up to par to a 7700K. I'm just going to sleep in the bed I made for myself and continue using this thing as-is.
Already starting to hear about Coffee Lake... So if I buy another CPU it might as well be that. It appears to be socket 1151 as well.