I have a 7 yr old boy whos right testicle has gone missing is this common or something to worry about?

Needs confirmation: There are some kids whose testis will retract back up into the groin occasionally but it is not good if it stays there.Your dr needs to examine the boy & possibly do an ultrasound to locate the testicle. A urologist or surgeon may be needed to bring the testis down & keep it down.Undescended testis can impair fertility later & have higher cancer risk over a lifetime.