no your dog does not need medical attention just get some tacky bar soap that you use to bathe and it will stop no big deal relax he will be fine also for the future your prt store or vet sells items that will make it stop bleeding faster
I've found using corn starch, pack it up into the nail, usually stops the bleeding quickly. It will only need medical attention if it doesn't stop bleeding after 15 minutes of packing and pressure.
You can alwys pick up a little container of QuicStop at a pet store. It's made specifically for these types of situation. I know it's probably scary when you do it for the first time because nails bleed, and bleed and BLEED! I don't think the dog feels the pain once the inital prick. It looks alot worse than it really is