After having an operation for inguinal hernia, if I masturbate a testicle will often shift up into my lower abdomen. Is this something to worry about?

Odd symptom. Any adult whose testicle goes into the abdomen at any point is a problem. A hernia operation is supposed to close off the tunnel a testis would travel on that side. If you mean it travels high in your sac, that is not as much a problem. You need to contact your doc if that is really true. .