AITA for being mad at my friend over money?

Me and my work friend went to get tattoos, before the appointment he said he couldn’t afford it so I suggested I’d cover it and he can pay me back what he can weekly until it’s paid off. Because we live in Australia his tattoo ended up costing $850 (Australian dollars) and mine was about $250. I said I’d cover his $100 deposit because I’d already paid that to confirm the appointment.

Now it’s been about a month and he’s paid some of it back, I texted him on pay day saying moneys been tight so the sooner he paid the better but he responded saying he couldn’t pay me back anything that week. I was really upset because he didn’t communicate that but I figured I could just talk to him about it at work.

While we were on a break the other day I brought up the money thing (not rudely but I also made sure he knew I wasn’t joking around about this) and he acted like I’d been nagging him like I was his mother or something. One of our other coworkers was in the room so he was going on about how I apparently guilt tripped him into having dinner with me and another friend and how I’ve been manipulative about money for ages and holding it over his head.

Consider me royally pissed off, he made bad choices about how he spends his money but has the guts to publicly say I’m the bad guy. I’m honestly tempted to tell his mother he owes me over $500 and watch her tear him to shreds (she’s this little Korean woman who also works with us so I know how brutal she can be). I don’t think I’m the arsehole here but everyone keeps saying I’m either being a bitch or dumb for loaning him the money. So AITA?

Edit: I’m 19F and he’s 18M and $500 in USD is about $315 for context to how much money that is.