Hi! One Of My Feet, The Left, That I Have

Hi! one of my feet, the left, that i have constant problems with is throbbing and has been for three days. It feels like I have a bruise inside in the middle of the bottom of my foot. I have a neuroma and have been diagnised in the past with plantar fasciitis. the planter fasciitis had improved so I had forgotten about it lately. It really hurts to walk on it.
I'm 66 years old, and I have osteoporosis. I need to exercize and am feeling desperate. What do you think this coud be?