Hey fletch. I believe from the information you provided that you may possibly have pulled a hammy. However, the injury happened last night, so it is also very likely that it was a severe cramp (I've heard that some cramps can take a few days to stretch out and relax).
If the injury, and same symptoms persist for an extended period of time (in my case weeks and months- definitely manageable discomfort though, not holding me back) it is likely a hammy pull. If bruising appears in the area in coming days, you can be fairly certain there has been a decent pull/tear of the hamstring.
In terms of rehab, you seem to be doing EVERYTHING right which is cool. Just keep doing what your doing and it'll either disappear in the next couple days, or in case of a muscular pull/tear, longer. Listen to your body, and keep implementing your rehab strategies. Begin light exercise of the area when you're ready again, and progress as usual- wish I could give you a magic pill, but I'm sure you know it doesn't exist.
All the best for the recovery,