Right side of the screen last 1/4 in no reponce to touch

So I get this zmax and it decides when it wants to work,I'll push to power button to come to the enter your pin and some times it lets me some times it won't respond, when it does come on that last 1/4 in on the right never works what do I do can't take it back got it from private party didmedirty@ yahoo.com