Take action:
Drain large blisters (more than 2,5 cm across): hold a needle over an open flame to sterilise it and use it to make a hole at the edge of the blister; gently squeeze the blister to drain the fluid through the hole; flatten the skin that covers the blister - don't remove it; wash the area with soap and water and apply an antibiotic ointment and sterile bandage; don't use a bandage at night; change the bandage at least once a day; call a doctor if there are signs of infection.
Read more on first aid for cuts, abrasions and bruises.