Can dvt present without any complications after one week, will the swelling subside without any treatment?

Risky: Surely the mortality rate from DVT isn't 100%. Some people get DVTs and get better all on their own without treatment. But the odds are a lot better if you take the proper medication. And some people do die from complications of DVT unfortunately.

Need a ultrasound.: The location of DVT needs to be clearly identified with a detailed ultrasound exam. Swelling subsiding or not does not mean clot or etiology of clot or new clots down the road need to be determined. In a 24 yo female risk factors include BC pill, recent long travel, inherited disorders or clotting, pregnancy, cancer related, autoimmine disorders. Some non DVT clots may also reguire blood thinners.

Yes and possibly: A DVT can be present for some time with minimal symptoms and no complications such as pulmonary embolism (blood clot in lungs), but will not usually resolve completely without treatment. If you suspect you may have a DVT, you should see a physician/provider, since complications can be life-threatening.