The 7th and 8th cervical nerves serve sensory function to this area. Therefore, it is possible that your problem could be anywhere from your cervical spine to the peripheral nerves. Without examining you I can not be more precise. Regarding the biceps tendon, this should not cause the problem in your fingers. What I would recommend is that you have a consult with a neurologist. The neurologist should be able to examine you and localize the problem more precisely. You may need a MRI of the cervical spine or an EMG (muscle/nerve) test. Good luck.
Had an EMG from shoulder to hand which showed no problem. They're now recommending a neck MRI altho I don't know how my neck could have gotten messed up during shoulder surgery. Let me know how you're doing. ***@****