How can I get rid of boil like scars on the back of my foot from wearing bad shoes?

Stop wearing bad sho. These heaped up scars at the back of heel is the result of tight ill fitting shoes.The best solution is to prevent them by wearing well fitting shoes.Sometimes people form a bursa at the site of friction.My advise is not to have any excision as there is not enough tissue at this site and you do not want another scar.Most of the time if you avoid pressure from the shoes it will improve.
FIrst of all... ...Replace the shoes, if you haven't already. Second, my guess, without actually seeing your feet, is that the "boil-like scars" are healing blisters. If that's true, they will heal by themselves, assuming you replaced the bad shoes with good ones. Just keep your feet clean and as dry as possible.
Options. It really depends on timing & extent. If new, time is your best friend to allow for scar maturation. If old, surgical options are available but limited in area as healing may be difficult due to minimal localized skin laxity & exposure to post-operative trauma . Intralesional steroids and topical silicone gel sheeting should be attempted for a minimum of 4-6 months. Scar massage may help as well.
Bad shoes. The first thing to do is the obvious - wear proper fitting shoes. Deep heat helps sometimes , but this may be healing blisters as another dr wrote. Time is your best friend there. See a podiatrist for an exam and advice.