What Causes Cranky Behavior Of An Infant After Giving Nurofen For Fever?

My baby is 4 months old she had her jabs yesterday morning and last night had a bit of a fever and was a bit miserable so gave her some nurofen today she has been a bit moany she went to sleep for 1/2 an hour and woke crying at a high pitch which ive never heard before she felt cool but sweaty should i be worried?