I experience this every time I self-treat more successfully with regards to injections.
It resolves and I consider it a result of being able to release tension in a way that was not possible prior to more successful self treatment of my neurological system.
I am well versed in releasing tension. I have practiced yoga since 1977 with varying degrees of intensity. I find Tai Che to be more effective although not as a self defence. I use this video when unable to manage anything more.