Personally, I wouldn't worry about it. A single application of seven, or any other garden approved pesticide doesn't pose any kind of meaningful threat. Repeated exposure over a life time becomes a different matter. I've used seven and many other chemicals in my gardening area. Don't use such now, or only use them very sparringly, but am certainly not going to waste my life force by worrying about residuals from past chemical use. When we first moved out here in 1979, I tore down an old mule barn that had not been used in at least thirty years. In the middle of removing the structure I got hit with a pleasant ordor that I had not smelled in two or three decades. It was the fresh smell of DDT. For some reason I always loved that smell, pretty weird I guess, but the odor brought back childhood memories of driving through the open crop lands in the fifties and early sixties, smelling the fresh spray of cotton poison (DDT). But anyway, there that cotton dust was, sitting within a few feet of where my current garden is. Probably many decades of pesticide use have been broacast on that soil. IMO time will heal the land and my current avoidance of chemicals probably makes my home grown veggies much better than the commercial foods which continue to be covered in fresh poison, plus have fifty year's worth of chemical residue in the soil. So rinse those plants, or not. Don't worry about it, just adjust going forward. That little bit of sevin is not likely to hurt anyone, and is already breaking down into byproducts that will be dissolved and washed away, and solids will eventually disburse to the extent that the slight long term residue will barely be measureable.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.