Brown urine after gym, urgent help

I started going to the gym 3 days ago , my arm muscles are sore and stiff and in pain, in the morning the peed dark yellow and now at night i peed brown.

i feel totally fine, but i am scared. it says brown urine can occur after strenuous exercise due to myoglobin being excreted through urine, but also says myoglobin is toxic to kidneys and can cause renal failure. i am terrified.

i am an otherwise healthy 18 year old male with no history of kidney problems.

Do i need to go to the ER right now, or can i wait until morning to go to urgent care? i am drinking lots of water. to try and dilute the myoglobin concentration. i don't want my kidneys to fail. please help me