Nope, nothing you can do about this. Just forget about it and move forward. Help other members or give good info to other and you will get a green rep.
The BEST thing you can do about Bad REP is NOT making a thread about it .. or posting about it Because that will just get you more Red Reps Like today, I got a bad rep, Didn't care (Altho there were some nasty words there) But then I got a Green Rep,.. From a Mod
Oh boo hoo someone gave me red rep, build a bridge and get over it you little weasel. Grow some cyber balls. etc.