As per your description it appears that pigmentation persist for longer duration in your case. It may be due to Atopy or dry skin. Good skin care required, use cetaphil dam moisturizer daily all over body particularly on legs , forearm twice daily. Use full sleeve cotton cloths always. Apply momate cream twice daily on patches for 15 days.
Next Steps
avoid mosquito bite by all possible means like full clothing, use of mosquito net
Health Tips
use good SPF > 30 sunscreen if you are not using full sleeve cloths , if going outside at least 30 minutes before and every 3 hourly if there is prolonged sun exposure.