Hi, I Opened My Car Door And Hit My Head

Hi, I opened my car door and hit my head pretty hard a week ago. I went to the er, they glued the cut together and gave me an ice pack. I now have a black eye and a lump still on my head, they told me I was fine going back to work. I went back to work two days later and every time I picked something up that had a little weight to eat I got dizzy. Should I have this lump checked out again?