What happens if you get a hematoma after breast augmentation?

The hematoma is a collection of blood in the pocket of dissection after surgery. It's a rare complication. If it's small it can be watched as it can reabsorb on its own, although there have been reports of increased capsular contracture (hardening) after this complication. If it is large (significantly more swollen on one side) or if it is rapidly growing (Expanding hematoma) the patient needs to be urgently re-explored, the clots removed, the bleeding vessel stopped, the pocket washed out with the triple antibiotic saline solution and the implant placed back.
The key is to try to minimize the chances of it happening: Making sure the patient is off aspirin, Motrin or other NSAIDs, off other meds that can affect clotting, off certain supplements like Vit E. Make sure the patient does not have a history of a clotting disorder. In the OR, make sure that the dissection is carried out carefully with good hemostasis with the cautery. Post-op make sure that if the patient has a history of hypertension that the blood pressure is well controlled. At home avoiding early vigorous exercise and very hot bath is a good idea.
I have specialized in Breast surgery for a quarter century, have placed over 8,000 implants and rarely see this complication.
JP RIOU MD FACS

If you develop a hematoma after surgery, that breast will be explored to determine where the bleeding is coming from and to stop the bleeding and evacuate the blood.  I hope that this helps!

There will be no long-term consequences from a hematoma after breast augmentation if it is surgically drained. Expected treatment increases the risk of capsular contracture.