Arman Tsarukyan is taking his fight against Dan Hooker head-on -- literally -- 'cause he butted his opponent right in the noggin during a tense weigh-in altercation.
There's some serious beef between these two guys leading up to UFC Fight Night in Qatar -- Tsarukyan wasted no time going after Hooker after joining the promotion ... and it only intensified in the days leading up to the bout.
The two came face-to-face on Friday .