I think it is worth a try to re-settle him. Oliver was the same, as soon as he learnt to sit up in his cot I'd go in there and he would be wide awake waving at me. (I would get so frustrated) how could this kid be wide awake and want to play at 2am!!!

I would just go in, lay him back down, say a sleep association word like 'nighty night' and walk out. I would only say 'nighty night' the first few times and then after that I wouldn't say anything. No word of a lie I've done this about 25 times in a row but eventually he would stop sitting up. If he started to get upset I'd pick him up, give him a cuddle and wait until he calmed down before trying again.

I did the same thing when he learnt to stand up in the cot.

Give it a go hun, I really hope it works