Dry skin brushing is really important to get the friction going to move lymph, plus clear dead skin cells.
The skin is an organ of elimination and this could just be the body trying to eliminate something!
My biggest question is, do they hurt or are they just visual irritations?
If there is no pain, then I would not worry about it.
If there is any pain, then I would discontinue the brushing until they settle down. You may wish to consider some bath soaking with various essential oils, epsom salts, and/or ACV.