What is the black line in eye obstructing the vision?

Hello doctor,

My left eye developed a black wavy line that moves around every time I try to focus, at times obstructing my vision. After consulting a doctor and after an eye dilution test, she confirmed that bleeding had occurred in my eye around two weeks ago and the black line I could see was the blood that had spilled. She sent me to a retina doctor who said he had to inject me in the eye. He did not explain the reason why and was a bit unwelcoming to the point that he did not give me a chance to inquire. He prescribed two drugs (Maxidex sterile ophthalmic ointment) and Ceprolen-D eye, ear drops). I have been using these medications since I did not have money for the injection. I can see little improvement but I am afraid it is not cleared yet. All I want to inquire is, what could be wrong with me? I underwent many blood tests and passed them all. I have never been in accident. All I have had is little sensitivity to light. Also I had been working long hours in front of the computer without anti-glare glasses before my problem started. Do I need the injection or is there a medicine that is more appropriate? I am 21 years old..Please help me out. Thanks