I'm working with 12V 6.5A power supply, should I be worried?
In short 12V is safe to handle.  Many power supplies have current limitation built in.  If you know what current will be needed for your circuit you can set the current limit to that value.  To do this set the current limit to zero amps.  Short the + and - wires from the power supply together, set the desired voltage and turn up the current to the value you need plus a little bit more for margin.  Then open the leads.  Now you have a supply that will only  provide the needed current and limit damage should a short occur.  

UL lists 60VDC as the maximum safe voltage and 30Vrms for AC.  If you stay below these values you should stay safe.  However, if you have ever shorted a 12V car battery momentarily you know that a strong spark is created.  That's because a car battery can delivery hundreds of amperes, so even when you are working at lower voltages caution and care when wiring your circuit should be observed.