Help with the pegs

Hi guys.Well i bought a new ukulele and when i tried to tune it a strange thing happend.I turned the peg but it went backwards when i let it go.(My pegs are on the back)I tied the screw a bit and it happend again but this time less.Well my question is:Is that cause of the string tension cause nylon strings need time to stretch or what?
Should i change the pegs or just take another ukulele?

If these are standard friction tuners, and you see or feel the button turn back as soon as you let it go, you're on the right track. Tightening the screw just a tiny bit at a time is the best course of action. I'd recommend starting with just one tuner that's loosening itself. Turn the screw clockwise about an eighth of a turn, tune it up. If it works without slipping, great. If not go another eighth of a turn and try again. Eventually, the tuner will hold. Then move on to the next one.

The reason you should go just a little at a time is that if you over-tighten, the buttons may crack. Getting there gradually assure you will not go too far.