Ricky Romance FIGHT -- The Urination Explanation

Ricky tells TMZ, it was just before closing time at Playhouse nightclub and his bladder was about to burst -- so he hit up the men's room ... but the line was ridiculous.

So, Ricky claims, he went out back to the smoking area and relieved himself against a wall -- at which point a giant hand grabbed him by the shoulder, and escorted him out through a rear exit.

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icky says he apologized profusely, pleading with the bouncer to let him back in so he could grab his things and leave -- but security wasn't having it. And that's when the slap fight broke out.