The pain on the left side of your rib cage
does`nt appear to have anything to do with the chicken pox
you had 20 yrs ago because you do not have any other symptoms. It looks like a musculoskeletal pain
. You should take a pain killer and apply some local analgesic
gel. Only if it persists, you should consult a physician or a pulmonologist who will examine you and ask for some relevant tests.