You may have overdone it. 30 minutes was probably too long all at once.
Broken up throughout the day would be better.
Short doses especially if it is something new for the particular area or muscle group.
What is your hydration like?
You may have toxins in your system from what your muscles release when getting unglued.
You need to flush your system of the toxins. Garbage out.
If you are at all dehydrated that plays a role too.