Was he interested in me or just a nice guy?

I had a seminar from my university last week. The first 2 sessions were online & the last 2 sessions were in person. I was assigned in a group of 4 with 1 other girl & 2 guys. One of the guys, let‘s call him Mark, had problems writing in our document so I helped him a little (this was during our online session)
On the first day of the session in person, Mark came a little bit late to class. He sat next to me since that was the only free seat. When he saw me he said "What‘s up" and smiled at me (this was the first time we ever saw each other in real life).
During those 2 in person sessions, Mark and I talked a lot. Not personal things tho, but Mark would ask me questions about the seminar, if I already had presented my solo project or he would just proudly show me how he scored 100% in a quiz.
At first, I thought he was just nice to me because I did him a favor in our online session. But those 2 days he was continually lowkey teasing me in a playful way. For example, we had to do a partner exercise and after I decided to do the exercise with the girl next to me instead of him, he was like "I didn‘t want to do the exercise with you anyway" while he was grinning.
While we were preparing our group presentation he playfully said "[My name], if I mess up you got me okay?". He also gave me a fist bump because we did our presentation "so well" (he didn’t fist bump the other 2 group members).
I also noticed him just randomly looking at me while we sat next to each other a few times.
On the last day I asked him something about the exam. Then he asked what my major is & I did too. Then he said "Okay [my name], take care, we‘ll see each other around" & gave me a fist bump. I saw him wearing a "love" necklace that day so I was wondering if he had a girlfriend but I obviously didn‘t ask him. I don‘t know if he was a little bit interested in me or if he was just a very nice guy? And why would he say "We‘ll see each other around" if he knows we don‘t really have any common courses?

Updates
26 d
After a little stalking, I actually found his Instagram but it‘s private. I tried to send him a request with 2 different fake accounts but he didn’t accept lol. I wanted to find out if he had a girlfriend. I don‘t want to send him a follow request with my real account because 1. we don‘t even have any mutual followers so it‘ll be kinda obvious that I had to stalk him to find his account 2. I feel like he might find out that I am behind those accounts
Was he interested in me or just a nice guy?
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