Is it possible that my left jugular vein may have bruised when i went on waterslide (twirling type) there is mild pain felt.

More likely a muscle: If you have pain when touching the area, it is more likley to by a mild injury to your sternocleidomastoid muscle. Try doing some mild neck stretching and if the pain persists or worsens within the next 10-14 days, you may want to go see your Primary Care doctor. Hope this helps. -Dr. Smith

Unlikely, but: Neck pain after going down a water slide is more likely to be due to a cervical sprain or strain from sudden twisting of your neck. However, without an examination it's not possible to diagnose your condition. Please see your physician if your discomfort persists