My nostrils are constant bleeding for 4 months now, as to my left nostril feels indented inside.what could cause this.

Probably dryness: Most likely the inside of your nose is dry assuming you're not using any intranasal medications. In some patients dryness creates an inflammatory condition so there is also congestion. Suggest saline to cleanse any mucous or crusts then sesame oil 3-4 drops each nostril if not, allergic to sesame. Do this 2-4 times daily. Compounding pharmacy might be able to get pharmaceutical grade oil- smells ok.