We miraculously managed to get a good deal that we could blow all our savings on to get this new HVAC unit installed about a year ago. In the last few days, it's suddenly started producing a sour smell, particularly in my room. Looking up the issue, all I see is people saying to call someone to get it cleaned because it's mold and/or bacteria build-up. I changed the filter, but the one that was there was barely dirty at all, so I don't think that was much of a fix.
I can't go into detail, but there's a lot going on right now and we can't afford much. We barely even have time to organize fixing something like this. But I don't want to take risks with our health.
Can I get some advice please? What would y'all do?
*also my god the youtube algorithm-fueled thumbnails that come up when searching for tutorials on what to do about this are truly horrendous, look at this shit, just straight up embarrassing

I’m your guy.
Couple of questions:
You might have a dirty drain pan and/or clogged drain pipe. You can check and clean these yourself. You’ll need a screw driver.
You can DM me if that’s easier.
Edit:
Thanks!
It sounds like cleaning the drain pan/pipe might not be too risky to do myself, I suppose I can start by checking a video tutorial for that.
One thing I do notice, however, is that the smell is more intense whenever the unit is running during the day. Also, I'm not 100% sure, but there's a chance the smell is (either only or almost entirely) emanating from the vent in my room. I don't seem to smell it as much in other areas of the house, but I haven't gone sniffing enough to be sure if that's true.
I’m going to guess that you have a traditional central air system, not a heat pump. And I’m going to bet it’s a clogged drain pipe or dirty drain pan. Canonical_Warlock left some really great info about cleaning evaporative coils yourself. Also if one room is smelling you can also try to cleaning the vents in that room. If you’ve got pets or kids things can get spilled/stuck in those vents and grossness ensues. Those are probably the most easy explanations for the smell that you can reasonably fix by yourself over a weekend.
If neither of those work then there might be something else going on. The evaporative coils could be icing over. The system may have low refrigerant which could lead to the coils freezing, melting, and growing all kinds of gunk. You will need a licensed HVAC servicer to recharge your system. Additionally your ducts might need to be inspected and/or cleaned. You may have an unknown leak somewhere.
Is it a minisplit or is it central air?
Central
I watched this video to find out about cleaning the drain line, it seemed simple enough so I marched down to the interior AC... unit... machinery... giant grey boxy thing to find the PVC pipe to uncap, but I don't see anything like this coming out of the unit I have. The closest thing is a long tube that comes out and snakes down into a much thicker, larger PVC pipe. Not confident that's the same thing. Thankfully I had the foresight to check before pouring out a cup of vinegar, at least.
Does that bigger PVC pipe go into the floor?
For the sake of keeping my info private, I'll DM ya some pictures I took
I found a YouTube link in your comment. Here are links to the same video on alternative frontends that protect your privacy: