I got a sensation like that when I first started, and I took a break - immediately! Even though I knew it was very mild, I was quite worried (like when you suddenly realise you have mislaid your *spare* dick, and are down to your last and only one).
Usually if you quit stressing your body at the first indication of strain, it make a fast and perfect recovery. If however, you keep on ignoring the signals, the result can be a very long-winded recovery. Or permanent damage.
The good thing about these injury threads is they remind everyone to take it EASY!
I'm fed up of having a signature!