Dealing with a scrape (cleaning a wound)?
The ocean is not sanitary! Especially around major cities, so if you were on a bike path, there is a good chance you are close enough to civilization to where the ocean is not good for your wounds. I grew up in a beach house in Hawaii and know that until the wound closes you don't want to go swimming, you can get it infected. Happened to my foot, frekn SUCKED! Samoans wash off in the ocean after they get tattoos, but they are not as industrialized as we are.

The sand itself is not really that bad, not as bad as the dirt that is mingled with it. Washing it out with clean water and covering it with that rag, as long as it didn't have grease on it, should have been good enough to get you home where you could clean it better. The problem you are having isn't so much with what you did the first hour or so but sounds more like what you did after you got home wasn't enough. Hydrogen peroxide is good, keeping it clean, make sure there is no sand in there. Band-aids are supposed to take the place of the scab, so that is why you are not scabbing up.

If you are sure it is clean and you keep it clean with fresh bandages you should be OK. Some wounds take 3 weeks to start to look better. If the skin around the wound looks red and swollen (as opposed to scraped up from the road rash) then you might need to break down and go to a DR. I hate going to the DRs more than the any one I know, but there are times when a bunch of people you don't know giving you medical advice just isn't good enough...