play with

6. VERB

If you play with an object or with your hair, you keep moving it or touching it with your fingers, perhaps because you are bored or nervous.     

• She stared at the floor, idly playing with the strap of her handbag.
  

... Cobuild

play with someone or something :

1. to play games with someone or a group. 

2. to toy with someone or something. 

• You are just playing with me. Can't you take me seriously? 
• Please don't play with that crystal vase.
  

play with something :

to use something in a way that is not serious or careful 

• She's playing with a dangerous drug. 
• The budget is just playing with numbers and doesn't make sense.
  

... http://idioms.thefreedictionary.com/play+with