PCR product should be a single band on an electrophoresis gel. If you found unexpected bands, modify the PCR condition to reduce byproducts. The purity of the PCR product affect the efficiency of protein synthesis because proteins can be also synthesized from PCR-byproducts.
If byproducts are unable to eliminate by changing the PCR conditions, excise the target band from the gel and purify the DNA. Excise the band from the gel without using ultraviolet light, which can damage DNA (i.e., impair transcription). Blue light may be used, but exposure time should be kept to a minimum.