A white lesion on the cornea of the eye is called Keratitis
and maybe either infective in nature or , in the case of contact lens
use, a sterile infiltrate. Since an infective kerititis is more devastating if left untreated or undiagnosed, most lesions are considered to be infective till proven otherwise. Your contact lens may be contaminated as may be your lens solution bottle. Replace the solution as well if you have not done so. If the lesion is sterile, replacing the lens or solution is not the answer. Start an antibiotic eye drop
such as Tobramycin
in the affected eye 6 times a day and an eye ointment like chloramphenicol at bedtime. If it is a sterile infiltrate, a combination eye drop preparation that includes tobramycin and a steroid such as dexamethasone
clears the infiltrate rapidly. This should be used for not more than a week. Refrain from using contact lenses till the lesion has healed completely.