Corneal Burns if treated promptly should take around 2 to 3 weeks to heal and if the corneal burn hasn't healed within 3 weeks you should see the eye doctor again to see if it needs treated again.
If not treated a corneal burn could lead to loss of eyesight or other severe eye injury.
Always wear goggles when dealing with chemicals or when around anything such as grease that may splash up into your eye to avoid damaging your eyesight.