if you reseam and cut: MAKE A VERY TIGHT SEAM!
Oh my God! I would not dare to do that even then. I works, but it is risky... It does work though, when the stitches don't have a chance to come undone.
Washing it smaller MAY work, depending on the material. That means that you wash it (realtively) warm and lay it flat to dry. maybe try a washing just regular (rel. cold) first. Some knitting shapes smaller then.
careful in (too) warm washing the knitting may suffer (structure of the wool). And if it is pure synthetic, that will not do much if anything.
Re-knitting is the best bet, but a lot of work.
Growing into it will not be a good idea either :D