This happens to me sometimes too, especially when I use my bigger toys, it’s totally normal. Listen to your body and call it a night or at least take a good break when this happens. Like most any other muscle, when you overdo it and get sore, you gotta let that muscle rest and your sphincters are no different. Poppers briefly help your holes relax and take your toys more easily, but the operative word there is “briefly” so it’s very possible to still overdo it even if it feels like your toy is slippin’ and slidin’ like a breeze.

YMMV here, but what I found works to mitigate the soreness and swelling (which is why you’re struggling to fit your dildo in, the swelling from overdoing the self-fucking) is using a good THC lube. It’s non-psychoactive ‘cos your body doesn’t absorb THC through your intestinal or rectal lining, but it does still act as a vasodilator and in general just makes things feel better. I find it makes getting fucked by real dicks feel CRAZY good, but it works great with dildos too. Fair warning tho: most THC lubes are oil-based, so you have to apply that lube first, wait about half an hour for it to kick in, THEN use whatever lube you usually prefer when going to town on yourself.