You have stated that masturbation has no effect on hair loss, However i cant see this being true. Castration prevents male patern baldness for people who are genetically predestined to go bald. This shows us that if our testes which produce sex cells enabling us to masturbate are castrated this cancels out testosterone inturn DHT and other androgens which may play a role in MPB. So if u no longer masturbate your ruducing testosterone and DHT dramatically. Which in a sense by not masturbating which castration prevents you from doing you are trying to create a castrated form. What i mean by this is that if i dont masturbate for a number of years i am helping stop part of the role that castration does. There is an undeniable link between masturbation and MPB, castration proves this by the fact that it stops us being able to masturbate proving that if we dont masturbate we will reduce balding dramatically (Or as far as not being castrated will take us).
Apparently I’ve struck a nerve with the former chronic masturbators out there. When you search for “masturbation” and “hair loss” in most search engines, this site comes up pretty high on the list. While that is good, it leads to waaaaaaay too many emails from people wanting to tell me how masturbation and hair loss are linked, then trying to piece it together with some flimsy logic. Please, please, please think!
It is normal for men to have sex often — daily, twice a day, twice a week. We are all different with our sexual habits and routines. Having sex with a partner or masturbating is the same thing with regard to the way your body reacts. If you are having sex often (with yourself or another person), then that is normal. Hair loss and sexual activity should not be related, but clearly you believe otherwise. This is not the forum to discuss this and if you believe it to be true, then show me the connection in a well controlled study.
My advice to you would be to go see a doctor to make sure there are no foreign bodies embedded in the wound and make sure there is no infection occurring. From the timing of this post, the window to have it sutured will be too late (>24hrs). If your injury caused separation of the edges of the scalp, your wound may heal with a scar, producing a small bald patch. If that bald patch bothers you, you can always get a small, minimally invasive Follicular Unit Extraction (FUE) hair transplant to cover it. If you see a doctor, he/she may determine that closing the wound may still have value, but the longer you wait, the less likely will be this scenario. 
You raise a valid point. Research can be biased, and you must consider who funded it and the methods used. A good example of this is the research conducted by the laser hair industry, as we scrutinized the methods and its results (see 
Damage to hair with heat from curling irons, ceramic hair straighteners, etc, can potentially make your hair brittle and cause loss due to heat damage, but it should not cause balding. If your hair grows back it can take as long a one year, as hair goes through cycles of growth.