Why did Yosef aggravate his brothers further by relating to them his dreams?
Seforno: Once again, he acted out of immaturity, based on his young age. 1
Rosh, Moshav Zekenim: He was a Chacham, and saw a clear prophecy. One who withholds (does not tell) his prophecy is Chayav Misah bi'Ydei Shamayim (Sanhedrin 89a). He said, it is better that I be in danger through people - maybe Hashem will save me [than to Vadai be liable to Shamayim].