Changing. propane tank for a forklift it slipped and slammed into my chest i feel fine didn't even experience anything but i heard the chest is danger?

Yes: Chest trauma can cause problems. ASsuming there is no penetrating trauma, there can be some irregular heart beat created. This hopefully would be short lived. More concerning over the heart is a rhythm disturbance which is life threatening. This is called commotio cordes and will immediate standstill of the heart rhythm and may be impossible to start.

Chest injury: Undoubtedly your chest wall was bruised, but if you're not experiencing significant chest pain,tenderness,New cough or breathing difficulties I wouldn't be concerned about serious damage.

Chest: The chance that you I'd any significant harm without any symptoms is very slim. Quit worrying and go on with your life. If you start having pain, shortness of breath or any symptoms in your chest in the next day or two get it checked out.