For the purposes of college admission in physics, you don’t have to go outside the courses offered at your high school.
Selective colleges will want to see that you took a challenging course load from what is available at your school, including the highest levels of physics and math available at your high school (and other sciences too, like AP Chem), and also including challenging courses in other subjects.
However… I do understand how it feels, if you’re really excited about a subject, and want to study it at every opportunity 
For any college class you might consider, I would be sure to take a very realistic look at how you would fit it into your schedule without negatively affecting your other classes and activities.
- Compared to high school classes, college classes usually have less time devoted to lecture, and more time required of students outside of class.
- A physics class may also include lab sections, discussion section, and substantial work outside of class on problem sets and lab reports.
- You might need to work together with other students on these things (and they would be students at the uni).
- College midterm and final exams are also often scheduled outside of class time periods; you would need to be sure you didn’t have any conflicts.
Also keep in mind that any grades in college classes will become part of your permanent college record. So be cautious about taking graded classes, if you don’t feel confident that you can do well in them.
10th grade for many students is a big step up in rigor. You might be very busy next year already (AP Chem is pretty time consuming in itself). So you might consider whether it would make more sense to take a summer class or do a summer program instead, or pursue your interest in physics in other ways.