Genuinely, I would go tonight if you can - otherwise you'll be in for a very uncomfortable night, and the sooner you are properly assessed the better.
The UTC / minor injuries is not an A&E. The entire point of them, is to be an alternative to A&E, leaving them to deal with the more urgent /...
I tore mine (gastro) desperately stretching to keep the ball in, in the 89th minute of a cup final, 15 years ago. I thought it was cramp at the time, given the situation - muscles stretched and under stress at the end of a hard game. It wasn't - and my team-mates' ham-fisted attempts to stretch...
Minor injuries unit, if you have one local @spongy - you'll be seen quicker - and they are geared up for this kind of thing.
If nothing else they'll be able to sort you out some crutches, and some strong painkillers...