Spectral location of individual OFDM symbols
The IFFT transforms a discrete signal to the time domain. Therefore, the input signal of the IFFT should be interpreted as a frequency domain signal.

For OFDM this means that the subcarriers are defined before the IFFT. The IFFT ouput is the time domain representation that will eventually be transmitted over the channel. Before it can be transmitted it must first be converted to an analog signal. Analyzing this signal in time domain, e.g. by viewing it on an oscilloscope, won't tell you anything about the subcarrier bandwidth.

To see the bandwidth of one OFDM subcarrier you have to analyze the analog signal in the frequency domain, e.g. by using a spectrum analyzer. If you modulate all subcarriers the spectrum will look nearly rectangular, with a flat top, because the subcarriers are close together and overlap. If you modulate only one subcarrier (all inputs of the IFFT are set to zero except one), the spectrum will be much narrower, its bandwidth approximately reduced by a factor that is equal to the number of subcarriers. And it will have a sinc-like shape.