Waking up screaming

This week, my 22mo has woken up every single night at around 1 or 2 am and is screaming at the top of his lungs. He normally sleeps straight through like a log. I’m not sure what the cause is? His current routine is up at 6.30 or 7, nap at 12.45-2, asleep for 8pm. I have wondered if there’s somehow another tooth coming (I thought we had them all though) due to him chewing his fingers a lot at the minute but I don’t know why it’d be the same time every night?