I smashed my front tooth in half a year ago and the cap that was put on it fell of the tooth is brown on the inside is it okay to leave it open for 2 or 3 days until i can see dentist i'm pretty sure the nerve is dead and no pain?

In general an injury to a tooth that has been there for six months. Can wait another couple days unless you have signs of infection such as pain fever.

If the crown fell off the sealant cement had washed out, exposing tooth material to oral bacteria. Another couple of days, if asymptomatic, is not going to make a difference. Please, however, see your Dentist as soon as possible. Do't keep putting it off.

It is ok to leave it open since it will allow drainage and preventing symptoms such as pain and inflammation. The tooth probably already exhibits pulpal necrosis (the nerve is dead) and thus there is no pain. As long as no inflammation results, you may wait couple weeks or even months until you have the time and money to seek definitive treatment. Do not try to close the area as pain may occur