I Was Masturbating With A Friend A Few Weeks Ago

I was masturbating with a friend a few weeks ago and after he cummed all over his chest I scooped it up and used it as lube to rub my penis with. i even scooped some right from the head of his penis. That friend just told me that he has HIV but that i shouldn't worry because he has it under control and its almost undetectable. Should I be concerned?