Heel Injury

I'm hoping someone can help.  Two months ago, I was playing basketball with my son (I'm 58, he's 28), the first I've played in about 5 years, although I was in great shape, running about 25 miles per week at the time.  I took a jump shot, and when I did, I felt a pain in the back of my right heal.  I tried another shot, had the same pain, but only sharper.  I was able to walk fine and have even run a few times since then.  However, now whenever I run or walk for long distances, I have discomfort (and eventually some pain) in the back of my heel and extending along the sole of my heel to about where it meets the arch of my foot.  I've tried resting it the past month, but nothing seems to have changed.  Also, when I climb stairs, it is painful unless I place my entire foot on the step.  I've also had chronic Achilles' tendinitis since having a bad reaction to a quinalone antiobiotic a few years ago.  Don't know if this is related to that.  Any help would be very much appreciated.  Thanks.