It is very unlikely that an under eye injury can cause such a swelling for so long. The possibilities of sinus congestion and allergies also need to be ruled out. However if it is a dermatological issue then botox injections, surgical uplift may be needed.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.