According to online records, Nick got busted Saturday morning just before 4 AM in Clearwater, FL -- where cops booked him on suspicion of driving under the influence ... noting he allegedly refused to submit to sobriety testing.

The exact circumstances that led up to the arrest are unclear for now, but they're logging this as a misdemeanor -- and they had Nick pose for this mug while he was being processed. As of this writing, he hasn't been released from custody.

On its face, it's a simple DUI arrest ... which, while serious, wouldn't normally be all that big a  deal -- especially if nobody got hurt. However, Nick had previously been involved in a scary car accident way back in the 2000s when he was just a teen ... also in Clearwater, FL.

It was a well-documented saga at the time ... Nick was driving with a Marine friend of his -- John Graziano -- who suffered a serious brain injury from the wreck ... but survived.

Nick, who was 17 at the time, ultimately pleaded no contest to reckless driving involving serious bodily injury. In the lead-up to that plea, cops had alleged alcohol was involved. Nick went on to serve an 8-month sentence behind bars in the aftermath.

Of course, the Graziano family also sued the Hogans over the accident ... and they settled out of court.

Nick doesn't appear to have any reps at the moment -- so we reached out to Hulk's camp for comment ... but no word back yet.