Plantar warts are not considered a chatzitzah since they are part of your body. They should simply be cleaned well, and soaked and softened during your preparations for immersion. Remove the medication prior to immersion and reapply after mikveh use.
You should bring your own water shoes, flip flops, or slippers to wear while walking around the preparation room and mikvah area. You should remove them just before entering the mikveh and immerse normally. Spreading the virus is less of an issue in the mikvah itself and more of an issue in the preparation area, shower, or bathtub.
Refuah Shleimah!