Dear patient, i want to know whether you had any venous catheter (central line) inserted in the left side of your neck during your hospital stay and how many days back had it been removed because you are on blood thinners espicially xeralto, there is a probablity that some oozing may have been taking place from the venous puncture site and that might be causing haematoma formation in neck giving rise to swelling ,pain and stiffness in the neck. So you immediately consult your doctor who had treated you for the lung clot and who had done your bipass surgery so that they can get ultrasound, doppler or any other required test of your neck done to find out what is exactly happening