New symptoms - should I worry

I was diagnosed with stage 2 breast cancer last year.  The cancer was removed and it had not spread to the lymph nodes.  I had radiotherapy for 5 days this year and am now on Tamoxifen for 5 years.  For the past month I am having pins and needles on the top of my left foot that has got worse and is spreading up my lower leg.  It never goes away and for the past few days I feel like my leg doesn't belong to me.  It is a really odd sensation.  Not sure if I should get it checked out or whether it could be a side effect of the medication.  I don't want to contact my Oncologist or Doctor unnecssarily.