1 testicle slightly harder than other?

hi, im 19 and i noticed that my right testicle is slightly firmer than my left one. its not painfull. it doesnt feel heavier and there are no lumps on it. my family has no medical history of testicular cancer. anyone any idea what this is? if it persists i will see a doctor, but i would like to see if it'll go in the meantime as i have very important exams for the next 2 weeks.