You can play with con of your primers but most of time you have to design a new one.

agreed with Alireza Mordadi.

Probobly your primer concentration is too much. If yo are getting the specific amplicon of interest, do a titration with your primers.

Redesign primers, decrease the amount of primers or change the polymerase.

One important approach to prevent or reduce primer dimer formation is by modifying the primers so that annealing with themselves or each other does not cause extension.

Thanks a lot to everyone.

You can try a temerature gradient for annealing temperature. That usually helps.

Thank you.

Go for hot start of PCR cycles

you could do a titration with your primers to delete the primer dimer.

Thank you very much for answering.

Do you use any form of dimer prediction when designing your primers?

We recently published a paper that compares the performance of freely available dimer prediction algorithms if you're interested in which performs best.

https://www.nature.com/articles/s41598-018-36612-9

Primer concentration won't matter if you use a Hot Start polymerase and have well designed primers that don't interact strongly at their 3' ends.

Yes I agree with Andrew Johnston. You can follow their publication.