Chris Brown sustained a nasty gash on his chin -- apparently a wound from a bottle attack -- after his entourage allegedly clashed with Drake's crew in a NYC nightclub brawl.  TMZ has confirmed with the NYPD that the two singers' crews got into a fight at WIP nightclub -- 5 people were injured in the melee. NYPD arrived on the scene after receiving a call between 4 and 5am. Chris and Drake were not present when cops arrived. We're told there were no critical injuries ... just bumps, bruises and lacerations. No arrests were made. After the fight, Brown tweeted a photo of his injury ... along with the message, "How u party wit rich n**** that hate? Lol... Throwing bottles like girls? #shameonya!." The photo and the message have since been removed from Brown's Twitter page. There are reports the two started throwing blows (and bottles!) over Chris' ex girlfriend, Rihanna, who Drake is rumored to have hooked up with. A few hours before the brawl, TMZ shot footage of Drake leaving the London hotel ... surrounded by some diesel-sized hired muscle. No word if they were involved in the bar fight, but wow ...  that would be scary.