In The Last Couple Of Weeks, I Have An Armpit

In the last couple of weeks, I have an armpit odor only on the left, whether I am working out, hiking, or not. This is new. It smells a bit like a "nervous" sweat odor, but always, only, from the left armpit. I don't think my right or left nostrils are detecting differently..... I am 72 and extremely active. No new pressures or stresses (I live in the mountains and hike most days). No change in diet.