My daughter is 3 years old and her platelet count is 118. should i be worried?

Sounds inaccurate: I think it is probably 118.00, which is normal.

Not so much...: 118 (meaning 118k = 118, 000) is lower than normal, but not so much (low end of normal is 150k). Did she have a sickness recently (a common cause of a transient lowering of platelet count)? In the absence of bleeding symptoms, i wouldn't be too worried. Rechecking in a month or so to make sure it is not trending down would be reasonable.If new bleeding symptoms, get checked immediately.