What happens if don't treat inflammation from a soft tissue injury in the foot until several weeks later? congested tissue? how do you treat it?

Start now: Ice, compression and rest. Although it may be congested, you are relatively healthy and your body will naturally remove the congestion over time. There is no quick fix, but ice, compression (use ace wrap), antiinflammatory medication and rest. Hope this helps.

Infection: Congested tissue weeks later after a soft tissue injury may represent infection or a cyst formation. Either will need to be examined by a health care professional. I would refrain from prescribing treatment without knowing more detail because i don't want you to delay being seen by a health care provider. Your may need antibiotics or even drainage if pus has collected.