With products like this (creams, gels, lotions etc), you should find a small picture of an open jar on the back, next to where the ingredients are listed. Printed on this jar is a number. The number is how many months the product can be used for after the seal has been broken.
I wouldn't think you would have any problems if it were used up within 12 months of opening. After that, I'd probably buy a new bottle.