Try carrying out a PCR that you know will work (for example amplifying part of a plasmid) and add different amounts of your tick DNA to the PCR reactions before putting into the thermocycler. If your DNA sample contains inhibitors it should inhibit the amplification of another template in a dose dependent manner.

I think you should choose more than a different dosage templates

Martin Craig Taylor , as far as i understand this approach, you are saying that i should amplify my plasmid ( positive control) with different set of primers.because i am using gene block ( syntheticDNA ) inserted into my plasmid as positive control.

suppose i will amplify my plasmid with different set of primers which i know will work but how can it determine that my sample contains inhibitors?

No what I am saying is that you should set up several tubes of your positive control, with its own primers and add increasing volumes of your tick DNA so you have a set of samples where each one has the same PCR reaction but the tick DNA is added as a suspected inhibitor. If your tick DNA does contain inhibitors then it will block the amplification of the control DNA. as you increase the amount of tick DNA added you should get less of the product from the control reaction if the tick DNA does contain inhibitors.