I think it might be a leaf-gall midge (Procontarinia matteiana) damage. Generally there are 16 species of gall midge insects which infest different parts of mango like leaf (Procontarinia matteiana), flower (Erosomya mangiferae), shoots and fruits.
The adult leaf gall midge lays eggs inside the tender leaves and causes small reddish spots initially. Later eggs will hatch and the galls will form on leaves (within a week). The matured maggot drops out and pupate in soil. This damage reduces photosynthesising capacity of leaves and also serves as entry point for anthracnose pathogen. The severely infested leaves may curl and drops off early.
Collect and burn the fallen leaves. Since they pupate in soil, deep digging the soil around the tree helps in exposing pupa to sun and other predators. Also mulching soil with suitable materials helps in preventing emergence of adults from soil. Spraying the aqueous extract of neem leaves powder (400g/10 liter) reduces the leaf gall midge population.
Appearance of raised spots or bumps (galls) due to leaf gall midge damage.
Adult leaf gall midge
Eggs are laid onto leaves causing small red spots
Your mango tree leaves are infected by gallmidge insects this insect live between leaf lemina only systemic insecticides can control it. If infestation is not severe hand picking and destroying of infested leaves will also help. over 8 years ago.