Took 2 Claritin (loratadine) in the same day by accident should I be concerned?

No emergency. Nothing adverse should happen. Read the label and follow their directions in the future.
Claritin (loratadine) Greetings. Taking 2 10 mg loratadine pills will not cause any problems except possibly extra dryness in your mouth. Although only once daily is approved by the FDA, 2x/day therapy is often recommended off label to help patients with hard to treat allergy conditions. I still recommend you use once daily treatment unless recommended by your doctor.
No. No need to panic, just be careful, at times it can be taken twice a day, but under doctor's supervision.