I have a 42 Sony flat screen it has a blue blob in the lower left corner what do I do to correct this?

Sony TVs has an Optical Block issue. If there is an issue with the optical block, then there will be green, blue patches or tint on the TV display. Try resetting the TV to the factory settings and try Power resetting the TV. Turn Off the TV and remove the power plug from the wall outlet for 1 minute and reconnect it and check the operation. If the issue still persists, then TV may require service. You can contact the Customer relations team and check for the available options. Sony had repaired free of cost for such issues. Hence, contact the customer relations.