Yesterday I noticed a fairly large bruise on the heel of my right hand just below my thumb. I don t remember hitting my hand recently and, since the bruise is approximately 1 - 1 1/2 inches long and maybe 1/2 inch wide and pretty dark in color I would think that I would remember what caused it. Now, today I recently noticed that there is a numb sensation over the bruise. It is a little tender if I press on the area, but I still get that numb sensation. I tried to do a little bit of research and did notice that a vitamin B12 deficiency can cause similar symptoms, and I have recently been diagnosed with the MTHFR genetic mutation. However I ve never experienced a bruise with numbness and would like to know if there is a need for immediate concern.