repotting during flower

im 3 weeks in should i repot for bigger yield?

It would just cause stress. You want to avoid stress for a bigger yield.

Should have repotted in veg.

If they are rootbound right now, go for it cuz you're not even half way through your bud cycle. Go up 1 size THATS IT ! Be gentle. Dont soak them too much after you transplant, give them 1/3 of what you would normally give. Also do it just before theyre ready for WATER. So however you do it, lets say you go 3 feedings and 1 water, after the 3rd feeding do the TP and wait until the pot is ALMOST dry. Ive done this and got away with no shock, just be gentle. After you TP, as I already said, give them just a minimal amount of water, MINIMAL. Ive done this and it worked out good, they took right away.

clicky here;https://www.rollitup.org/general-marijuana-growing/345245-transplant-without-any-stress-soil.html

My two cents I agree with Smrt, in my container grows I usually step up about the 2 or 3rd week after I start the flower cycle. This about the time they seem to get root bound and I get to add fresh compost around them. Of course I am a bit of an oddity but it works for me. I also use SuperThrive in the water after transplant this seems to help with any shock problems. But being gentle is the key, right before they are scheduled for watering the plant will slide out neatly and allow a smooth TP without shocking the girl. Good Luck and Happy Growing