I Have Been Prescribed 500mg Of Levofloxacin For 7 Days

I have been prescribed 500mg of levofloxacin for 7 days for a respiratory infection. I am 62 years old & I have one pill left to take today. about 2 days ago my left arm area where it meets my shoulder feel funny & a little sore when I try to raise it. I know this can cause tendon problems, & I'm concerned that that may be it. I called pharmacist & they said if I was to have tendon problems it would have occurred about the 1st or second day. He said if I don't take my last pill I may get my infection back. Should I not take the final pill or chance it?