Bony structure under medial malleolus bilaterally, no pain w/ compression, tibial nerve is palpable, mild flat foot. Could it be misaligned calcaneus?
Hyperpronated. You're describing foot structure consistent with being hyperpronated.This is associated with flat feet. You don't have to be that flat-footed to be pronated. Your bone structure under your medial malleolus will be prominent. I doubt you're feeling your tibial nerve, it's probably your post. Tibial artery. Being hyper pronated could lead to a lot of problems. Address this. Are you symptomatic?
Tarsal coalition. A bony protrusion under the medial malleolus maybe be a sign that you have a tarsal coalition of the ankle bone (talus) to the heel bone (calcaneus) especially if the flatfoot (pes plunus ) is associated with stiffness of inversion and eversionof the hind foot. A plain xray and or a MRI or ct scan of the foot will confirm what the situations.