If it’s new shortness of breath or chest pain , particularly the crushing variety that feels like something is sitting on you, do not pass go, do not collect money, straight to the ER. Same goes for sudden severe lower back or abdominal pain or sudden heavy bleeding out of your orifices (more than a super maxi-pad full every two hours if you’ve got that genital configuration). There’s a few other little things like a continuous erection more than 4 hours. Also you should learn the signs of a stroke (Google “stroke” FAST). If you’re not sure, look up the local ERs number (not 911) and ask for the “triage nurse” and ask them.

If it’s been going on / steadily getting worse for over a month it can (probably) wait one more week if that’s all it will take to see your primary care physician or see a specialist.

If it’s sudden but you know exactly what you did like if you pulled a muscle or sprained a joint at work or cut or burned your arm while cooking (I specify arm, if you cut or burn your hand, face, genitals, or foot, measure how big it is and call that triage nurse) or if you forgot to pee after sex or did it with somebody sketchy and now it hurts to pee, go to the urgent care. Or if your petri dish of a preschooler brought home something and you’re not sure if it’s strep but you almost definitely need a note for work. Or if you have an old cut but now it’s looking puffy and oozing weird liquids (but it’s still localized to that one little area, you don’t have a fever or anything). If you can look at it and already have a general laymans idea of what they’re gonna do to it, go to the urgent care.