The young model is apparently having a great time in Italy, but the love scar has us wondering who left it there? Anwar has a long hookup history with fellow models ... and guess which famous former flame was also in Milan? Kendall Jenner!

Remember, back in the summer, Anwar and Kendall were sucking face at an after-party.

He's definitely not trying to hide the evidence of a steamy night with someone -- so, maybe it was Kendall's handiwork ... or maybe he's just letting her know she missed out.

One thing's for sure ... Anwar's gonna need a cold spoon, 'cause that hickey's not going anywhere soon.