Identify hematophagous insect
This is an "aphid lion", a larva of a lacewing (family Chrysopidae). They eat aphids and other small animals, not blood, but are capable of biting humans. Here is a text about that (seems reasonable even with the silly title). It also says that "When a lacewing larva bites a human, it’s likely that any persistent itch or redness is due to the saliva injected at the site of the bite" so that would explain your pain.