This could be as simple as a muscle tear (doubtful)
or as serious as sciatica (probable)
or possibly even a blood clot (unlikely, but possible).
I'm no Chicken Little, but severe pain and numbness is something I think a professional should take a look at. If nothing else, they help you get past the pain and on the road to recovery sooner. At my age(yours too), I've learned that it's better to address medical issues sooner rather than later to reduce my long term suffering.

