Ok first of, firearms are not "registered" as they like to portray on CSI and such. When you buy a firearm you fill out a form to make sure you qualify and are not restricted to own firearms. You, being under 18, can not purchase a firearm legally so your mother had to. Once you turn 18, your mother can "gift" the firearm to you and that will be that.
And as to my comment to your friends "playing" with your firearm, you yourself said that you were surprised at the unsafe conduct in which they were handling it. First off, a firearm is not a toy to be "passed around" to all your buddies to awe, admire, and fondle. It is a serious tool which is to be handled in a safe and KNOWING manner. You yourself already knew that none of them had any experience with firearms and, even at your young age, you should have known better. Being a firearms owner comes with great responsibility and the absolute need for common sense. Your "buddies playing with it in your house" is not common sense. If you wish to show your new weapon off, take them to the range, make sure that the weapon is safe, instruct them in the proper and safe handling of said weapon BEFORE they lay hands on it, and make sure that the muzzle is always pointed DOWN RANGE. Simple as that.