Tires,Service tire monitor warning, tire pressure a bit high

My car has gone around 85,000 miles. When I drive the car for 80 miles approximately, the dashboard shows the service tire monitor warning illuminated. I've been driving on the tires that I changed 8,500 miles ago. The other day, the warning flashed a bit and stayed on. I had the tire pressure checked. The recommended is 35 as far as I know, and my tires had 38 on average, except for the front left one that was shown blank. What do you recommend I should do? Is it safe to drive my vehicle? Thank you.