Thanks for posting your query.
The lump you are feeling may be a lymph
node which is lying over the location of your carotid artery
thus your attention is drawn to the pulsations.
Pulsating lump in the neck might be due to Carotid artery aneurysm
. Rarely the pulsations from the carotid artery can be transmitted to a swelling adjacent to it, if it is made of soft tissue
I suggest you to get an Ultrasound
scan of the neck done. This will surely provide details on the swelling and its relations making possible to identify the exact pathology easily.
I hope this information helps you.
Wishing you good health...