If my 19 mouth old son fail down the stair what should i do? but he is not cry.or bleeding he act the same

If he acts ok: no bleeding, no head injury, no loss of consciousness, no vomiting, no ear or nose bleed and acting normal, may wait till tomorrow and see your pediatrician

Monitor closely: Serious injury following a fall is usually apparent shortly thereafter. In the absence of bleeding, vomiting, behavior changes and obvious pain, close monitoring is usually appropriate. Symptoms that warrant evaluation include multiple episodes of vomiting, extreme sleepiness, refusal to walk or significant bruising.