Hi thanks for your question
You have developed hematoma
(collection of blood under skin) on your head after you got hit on it by door screen. This hematoma has got infected.
Since the infected hematoma is big,
It needs to be drained. You’re advised to consult some surgeon to get your puss drained.
And take antibiotic like leofloxicin to control your infection,
If you’re having pain
You can take analgesics (pain killer).
Hope I answered your question.