Oh no, will this be a problem

I screwed up, after my last grow I didn't change my light timer so my new plant has been on a 12 / 12 light schedule. After a month or so I noticed the plant looked like it was flowering, duh! I have switched it back to 18 / 6... Is it doomed or will it be stunted in growth?

what would I do without you guys?

what variety is it? an indica dominant plant is going to be harder to pull out of flower, I would use 24 hours until it's reverted. but if it's a full 4 weeks in it might not, or might just get really confused and stall out for a while