deltoid pain - am I doomed now?

I was trying to push my limit in the holidays just passed in order to prepare me for a nearly-5 km race coming next Sunday, then reduce my training load (while keeping the intensity) this week leading to the race. My normal training amount is 12 - 15 km / week, about half of them high intensity. On April 21 I swam 5.3 km with a group. As the group was slightly faster than me, I basically swam at an intensity of 1.5 km race the whole way, with a few stops between, while still feeling strong towards the end. There was no ill effect at that time. Afterwards my motorcycle failed to start. As that day was a holiday and I was in a rural area, I thought my best action was to push-start it and rode it back to the city, and wait after the holiday passed for maintenance. However, as I had no experience in that, I tried pushing it for an hour, with a near-success in the middle but failed again once I attempted to give power, and ended up exhausting myself which only succeeded with help of another. Although I was exhausted there was still no ill effect. After the night, on April 22 morning I felt pain at the lower part of my right deltoid, which affected me when I tried to raise my right arm. However in the afternoon the pain lessened and the range of motion was basically restored with very little pain, so I still continued my plan to swim with my coach at low to medium intensity for him to instruct me. I did not feel painful when swimming and the coach saw my stroke improved initially, and to attempt to lengthen my stroke, my coach put paddles on me for some distance (about 1 km) and my stroke really lengthened immediately after removal. The total amount of swimming was 5.7 km, i.e. 11 km in 2 days (as I am preparing for another race of similar length in July). My pain didn't appear again in the evening and I could use my arm normally. However, after I went to sleep, in the middle of night the pain appeared again and got much more intense, and today morning (April 23) basically I could not raise my right arm at all, and I could not extend my right arm to the left, and had to use my left arm for some common tasks, like lifting a full teapot. I am now very worried if I really injured myself over these 2 days. I originally planned to do another squad session today Tuesday evening, then rest for 2 complete days, then do a squad session on Friday morning, rest for another complete day then do the race. Now I am icing it while I'm in the office. As I don't have much experience in serious swim training, I have a few questions now: What's the likely cause of my deltoid pain - swimming or the attempt to push my bike for an hour? If I really hurt my deltoid, why the pain only appeared at night? Am I better off to skip today's evening squad session even if the pain lessened / disappeared and ROM restored by the afternoon?