I can't profess to having a ton of experience or knowledge of PWV (Pulse Wave Velocity) - beyond cursory knowledge and having the Withing Scale and see the daily record of the value. But I can tell you that for the past few years I've tracked my HRV (Heart Rate Variability) extensively and specifically have paid attention to hard workouts, inflammation and injury. Stress due to over exertion of injury can definitely negative impact HRV (lower HRV) and can also inversely raise your daily resting heart rate.
In fact, HR and HRV are usually inversely proportional (low heart rate tends to = high hrv which is good). And, stressors like too much alcohol (e.g. a bing night out with friends) can definitely raise HR and lower HRV for a 24-48 hour window.
Now, back to PWV. I'm not certain how the Withing scale can calculate arterial blood flow since it's just using bioimpedance. But, I did see a reference to there being a strong correlation between high PWV values and low HRV values (See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504149/).
So, again without having too much in depth knowledge of PWV, I wouldn't worry about a short-term increase being an indicator of any longer term heart health trend. More than likely you body is dealing with stress on multiple fronts, and as a result your parasympathetic nervous system / vagus nerve has downstream effects on increased heart rate, lowered heart rate variability and that computed/derived value of the PWV.