One of my testicles is slightly larger than the other. should i be worried?

Testicular asymmetry: There can be some variation in size between the testicles. If you have significant variation, or if the change is recently noticed, it is worth getting checked by your physician. Atrophy of one testicle can cause one to decrease in size, or the development of a testicular infection or tumor can make a testicle larger. Other problems such as hernia, hydrocele, varicocele or cyst may exist as well.