Why does my coworker like to bite me?

This really hot-blooded Columbian (m) co-worker and I (f) have a kind of flirty relationship at work (bar). Everything is innuendos and the last few weeks its him having both hands on my hips to pass me, which my other male colleagues have never done. Recently though, when we're working together and he's close behind me he'll bite my arm while passing me. A little hard and its definitely hot.

Why does my coworker like to bite me?
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