I expierienced the exact same dizziness you had, when I returned from my very first cruise. It was even shorter than yours. It was a 4-Day Bahamian cruise onboard RCCL's Sovereign of the Seas. Just like you I was concerned. Maybe not to the point of going to the ER. The dizziness lasted for almost 8 days, in my case.
During that time, I was bumping into my co-worker's on the job (especially when passing them in confined/close spaces). I wouldn't have been surprised if my boss gave me a breathalizer test. I could not put-on my pants without sitting down first, or else I risked falling over when trying to balance on one foot.
On the evening of that 8th day following the cruise, I went to work-out at my local gym. After a session on the StairMaster, I stepped-off the machine and immediately noticed a significant decrease in dizziness. I can't say whether the StairMaster will work for anyone else expieriencing this form of dizziness; but it did for me.
I have heard people describe this dizziness as "Sea Legs". I have heard old sayings suggesting that sailors will stagger and wobble for a few days after returning to port. I have even watched a TV program where some people are afflicted with this dizziness, where it becomes chronic and stays with them for a very long time. The doctors called that condition "Disembarkation Syndrom". Fortunately, it is rare.
Like I said, the dizziness began to fade after 8 days, especially after my StairMaster workout.
When I returned from my second cruise, I did not expierience any of the dizziness at all. On my third cruise, I expierienced the dizziness a little, but it only lasted for 3 days.
Upon reflection, I realized that on my first and third cruise, my cabin was all the way forward, near the bow of the ship. On my second cruise, my cabin was exactly in the middle of the ship (midship). So, maybe the location of your cabin can affect whether you will expierience this dizziness upon returning home after the cruise.
I definetly heard that the cabin location can play a significant roll in preventing sea-sickness (which I never had). And that people whose cabins are located midship have less of a chance of becoming sea-sick (due to the greater stability and less motion). And maybe the same is true with this post-cruise dizziness?