Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services after a chest injury if you have new or worsening shortness of breath, severe chest pain, fainting, confusion, pale or clammy skin, or a very fast heartbeat.
These symptoms may indicate major bleeding, a collapsed lung, or shock.
Seek emergency help after recent chest surgery or a chest procedure if breathing suddenly becomes difficult, you feel faint, or chest pain is rapidly worsening.
If you have already been treated for a hemothorax, obtain prompt medical advice for fever, increasing breathlessness, worsening chest pain, redness or drainage around a chest tube wound, or coughing up blood.
These may suggest infection, recurrent fluid, or another complication.
Routine follow-up is appropriate when symptoms are steadily improving.
Keep planned appointments for examination, imaging, blood tests, or wound review even if you feel well.
Every sign above is quoted from the sofidex article on Hemothorax. If you are not sure, err upward — it is always reasonable to be checked.