swollen, itchy knots on feet

I have been getting these swollen, itchy knots on the bottom of my feet at random times.
It seems to have become more noticable since the birth of my first child 4 years ago. They show up after I have settled down for the night and stay swollen until later the next day.
The only thing that seems to alleviate the itching and buring is 50mg Benedryl. I can go months without having one and then I’ll have three in a weeks.
I cannot seem to place them with a certain activity or time of month.
I usually wear sneakers because I am a nurse, so I am on my feet for 12 hour incriments.
These never happen at work usually when I am at home with my children on a day off.