Recently a coworker has been complaining of neck pain and asking me to help him with it. I think it is meant to be completely platonic but i get the feeling there is more to it. I have refused multiple times saying no but i was cornered in an office recently and felt like i had no choice. I am very uncomfortable but now that i have done it i feel like i cant say no. This co worker direct reports to my boss but is a higher position than i am. I don't want to go to HR as i feel it will be made into a huge deal and I will be labeled as "that" girl. How do i tell him I'm uncomfortable while avoiding the blowback of HR and avoiding follow up questions from my coworker?