I applied tomato and lemon juice on face directly. and after that my skin became reddish and more reddish pimples came on it. how should i treat it?

Danger: First clean your face with a gentle soap and warm water. Second, never, ever do this again. Third, your body should heal on its own without using any more solutions or creams. Just let it be. Never put acid on your face again. Tomatoes and lemons are acid.

Stop using it: Both fruits are acidic and cause skin irritation and may even cause infection if contaminated. Try some Hydrocortisone and see if this helps. I don't think these will improve your skin complexion even if they are not irritating.

See a dermatologist: Why would you apply juices to your face? You do not indicate if you do this to treat something. Was your face normal before this? Do not repeat the juices on your face. Wash with hands only. Warm water. Mild soap such as dove. A skin dr can help you.