Small red pimple on head of penis. Used a condom during sex a week ago. This appeared yesterday. Get tested?

Various causes. It can be simple irritation or it can be due to Human papilloma virus infection(warts) , donovanosis , chancroid. A simple urine test will not help differentiating the bump. You will need to see a Dermatologist or a specialist in STI to diagnose your condition. They will clinically examine you and rule out the STI.