That's a common symptom of worn valve guide seals and / or worn valve guides. Replacing the seals is a relatively easy and inexpensive job. If the valve guides are shot then it needs the head removed and machined. If it only smokes at start-up and not noticeably at any other time, then it's probably just the valve seals.
When the engine sits for awhile, oil on top of the cylinder head [which is normal] leaks past the worn seals, down through the valve guides and into the cylinders. That is what smokes on start up but once it burns off you see little if any more smoking. To replace the seals requires removing the valve cover[s], removing the valve springs and retainers and replacing the rubber seals. It's not a job for an inexperienced person lacking the proper tools including a valve spring compressor.
If you don't fix it, the cylinder or cylinders that have the problem will keep coking up with the residue of burned oil that at minimum will foul the plugs, may cause pre ignition or detonation or missing, and at worst eventually cause the valves to not close properly, reducing the engine compression and performance further.
I hate to say it but you probably just bought a pig in a poke. Hopefully not. GOOD LUCK