You definitely have a pinched nerve and while it's not an emergency you should get it checked out this week. As for stretching... won't help to stretch the arm. It's most likely that the pinch in in your lower neck area or if it was cold you could have "frozen" the nerve where it is close to the surface of the elbow. If the latter is the case... it's just a time thing. If it's the former, the most important thing for you right now is good sitting and standing posture. You need to lengthen that neck out and get your shoulder blades back. The best way to do this is to imagine that there is a helium baloon attached to the top of your head and that it's pulling you upward. It's also good to avoid sitting as much as possible because our posture tends to be significantly worse in the sitting position.
And make sure that you have a bike fit done.
Hope that helps.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
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