I'm bisexual and 'straight' friend grabbed my crotch jokingly

After a trip to London with friends I was waiting with one of my friends. He knows I'm bi-sexual and I assumed he is straight but he jokingly flirts with me to joke at the fact I'm bi-sexual and I really don't mind.
He started with his hand on my chest and ran his hand down waiting for me to stay stop. I thought he was bluffing and he touch my penis, further to my balls and grabbed it . He laughed nervously afterwards saying that was weird and how he thought I would say no. So I'm feeling confused to wether it was that much of an accident or wether he was trying to do something else.