Found this here in AZ while on a hike when it was just a tiny seedling lying on its side. This is after approx 1.5 years of growth. It leans very easily when watered and placed directly at the window. Has circular as well as flatter areas of its column. Anyone help?

A hike through the neighborhood park or in the mountains? It would have done better if you had left it outside. Its do etiolated, its impossible to say what it should look like. When it pokes you, do the spines hang on or slide back out of your skin easily? The only cactus I can think of that might look like that is a cholla.