It could be varicocele
Thanks for the query.
Naturally there is cluster of veins at the top of each testis to help keep temperature of gland lower needed for sperm formation.
When such veins get dilated which is quiet common, one get varicocele and one can feel pulsations.
Investigation of choice is ultrasound
with Doppler study.
Minor cases might not need treatment as such.Few patients need minor surgical procedures to correct this.
I would recommend a visit to doctor and get investigations done , so that further course can be planned.
Hope this answers your query.Please ask if there are doubts.Regards.