I have what feel like spasms in my left arm. It is like when a blood pressure cuff is too tight on your arm...Not really painful, but very very uncomfortable. The tightness, tingling etc comes and goes all day and night. Also, the tip of my left pointer finger is numb. This has been going on for over two weeks. I took flexeril and naproxon and it doesn't stop it.
The numbness in your index finger is due to compression of the nerve that innervates it. The compression could be in many different areas, from the finger itself, the carpal tunnel, at the elbow, in the upper arm, at the shoulder, or even in the neck.
Since you are having the tightness feeling in the upper arm, that would be the most likely area for the compression. However, with just the description, it is not possible to determine exactly what it causing it.
If it continues, you should see your physician for an evaluation to determine the etiology. Good luck.