Hi Just Returned From Disney 4-25 To 4-29. I Noticed

Hi just returned from Disney 4-25 to 4-29. I noticed small red bumps shove my ankles. All went away except my left ankle now has a large dark red splotchy area. What can this be? Walking in Disney 10-12 hrs a day for three days in 90 degree weather. I'm 51 years old. Also was in pool and hot tub at resort for two days.